The invention relates to a belt drive arrangement for an internal-combustion engine, comprising a drive pulley, which is driven by a crankshaft of the internal-combustion engine; a first output pulley, by which a first auxiliary unit can be driven; a second output pulley, by which a second auxiliary unit can be driven; and an endless belt, which has an inner face and an outer face opposite the inner face and, as a continuously variable transmission, loops the drive pulley and the output pulleys at least in sections. Furthermore, the invention relates to an internal-combustion engine having such a belt drive arrangement.
In current vehicle construction, a fairly large number of auxiliary units are necessary which are not or only to a limited extent required for the forward movement of the vehicle. Such auxiliary units are, for example, the cooling water circulating pump, which circulates the coolant of the engine and thereby contributes to the automatic control of the engine temperature; the generator or the alternator, which are required for supplying the electric onboard power supply system; the refrigerant compressor, which is used for the operation of the air-conditioning system; hydraulic pumps for the operation of a power steering system; ventilators for the radiator, etc. The auxiliary units are driven by way of drive pulleys or drive wheels of the crankshaft of the internal-combustion engine. In current motor vehicle construction, belt drives are used which transmit the driving power from the crankshaft to the auxiliary units. Deflection pulleys are required for ensuring a sufficient looping around the drive pulleys of the auxiliary units. Only if the belt sufficiently loops around the drive or output pulleys can a sufficient adhering contact be ensured between the belt and the drive or output wheel and, thereby, a sufficient transmission of torques and powers. However, such auxiliary drive arrangements known from the state of the art have the disadvantage that the use of deflection pulleys increases the expenditures for the mounting and, in addition, has a disadvantageous effect on the space requirement of the engine.
Based on this state of the art, it is an object of the invention to provide a simplified method by which the disadvantages of the state of the art can be overcome. It is a further object of the invention to provide a belt drive arrangement or an internal-combustion engine having such a belt drive arrangement, with reduced mounting expenditures and a reduced packaging requirement.
These and other objects are achieved by a belt drive arrangement for an internal-combustion engine comprising a drive pulley which is driven by a crankshaft of the internal-combustion engine, a first output pulley by which a first auxiliary unit can be driven, a second output pulley by which a second auxiliary unit can be driven, and an endless belt. The belt has an inner face and an outer face opposite the inner face and, at a continuously variable transmission, loops the drive pulley and the output pulleys, as least in sections. Furthermore, the inner face of the belt loops the drive pulley and the first output pulley while physically contacting them, and the outer face of the belt loops the second output pulley while physically contacting it. In other words: with its inner face, the belt touches the drive pulley driven by the crankshaft, and a first output pulley driving a first auxiliary unit, and, with its outer face, touches the second output pulley, by which a second auxiliary unit is driven.
Furthermore, the looping of the output pulley may take place in a power-related manner, the first auxiliary unit, which is connected with the first output pulley, having a higher power, and the second auxiliary unit, which is connected with the second output pulley, having a lower power consumption. The higher the power consumption of an auxiliary unit, the higher also the load torque which this auxiliary unit generates in the belt drive.
According to the invention, the belt therefore loops drive pulleys with its inner face that are connected with auxiliary units representing a high load torque. Output pulleys, which are connected with an auxiliary unit that generates low load torques in the belt, are looped by the outer face or by the back of the belt. This has the advantage that a particularly space-saving belt drive arrangement can be implemented, in which case additional deflection pulleys are not necessary. This also results in a reduction of the overall weight of the engine as well as of the costs. Furthermore, frictional torques are reduced, which has an advantageous effect on the fuel consumption and not least on the CO2 emission.
In addition, a tensioning roller may be arranged in the circling direction of the belt behind the second output pulley, which tensioning roller is looped at least in sections by the outer face of the belt. As a result, the auxiliary units may be arranged such that, at each unit, the looping angle is adapted to the power consumption or the load torque of the unit. This becomes possible by the positioning of the tensioning roller between an auxiliary unit generating a low load torque and an auxiliary unit generating a higher load torque. The function of the tensioning device in the looping direction behind an auxiliary unit with a low power consumption is made possible by the low induced load torque that is generated by the auxiliary unit.
Furthermore, the tensioning roller may be arranged between the first output pulley and the second output pulley. Such an arrangement of the tensioning roller in front of an auxiliary unit with a high load torque has the additional advantage that, in the case of a maximal loading of this auxiliary unit, the looping at the pertaining output pulley is increased. In other words, when the load torque of the auxiliary unit is increased, the belt is lengthened. The tensioning device adjusts and thereby increases the looping at the output wheel of the pertaining auxiliary unit.
In addition, a third output pulley is provided which is connected with a third auxiliary unit, the third output pulley being looped by an inner face of the belt.
Furthermore, the belt may form an essentially L-shaped circling path in the installed condition.
The first auxiliary unit may be a generator, and the second auxiliary unit may be a cooling water circulating pump.
Furthermore, the third auxiliary unit may be constructed as a refrigerant compressor.
In a further aspect, the invention relates to an internal-combustion engine for a motor vehicle which comprises an above-described belt drive arrangement.
In the following, the invention will be explained in detail by means of the description of the figures. The claims, the figures and the description contain a plurality of characteristics which in the following are explained by means of embodiments of the present invention described as examples. A person skilled in the art will also consider these characteristics individually and in other combinations in order to form additional embodiments which are adapted to corresponding applications of the invention.